The present invention relates to the field of hydraulics, more particularly, positive displacement hydraulic pumps and motors having gerotors, gears, or vanes.
Positive displacement pumps and motors that include gerotors, gears, or vanes have inherent volumetric losses due to the side clearances built into the mechanism. Side clearances exist between the rotary element or fluid displacing mechanism (gerotor, gear, or vane) and the axially adjacent members, usually a housing or end cap wall. The volumetric losses are a function of the side clearances to the third power. Thus, the volumetric losses are greatly affected by the side clearances. If side clearances can be minimized, volumetric efficiency greatly increases. However, manufacturing tolerances and deflection typically dictate the side clearances and limit efficiency.
Therefore, a primary objective of the present invention is the provision of a positive displacement pump or motor with improved volumetric efficiency.
Another objective of this invention is the provision of a positive displacement pump or motor having near-zero side clearance.
Another objective of this invention is the provision of a positive displacement pump or motor having a layer of abradable sacrificial coating material applied to the housing wall adjacent the rotary element, the coating wearing-in to establish a minimal side clearance and thereby high volumetric efficiency.
Another objective of this invention is the provision of a positive displacement pump or motor that is economical to produce, easy to assembly, and reliable and durable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims that follow.